A101421 Numbers which are the sum of two positive cubes and divisible by 7.

28, 35, 91, 126, 133, 189, 217, 224, 280, 539, 637, 686, 728, 756, 854, 945, 1001, 1008, 1064, 1358, 1456, 1512, 1547, 1729, 1736, 1792, 2198, 2205, 2240, 2261, 2331, 2457, 2709, 2926, 3059, 3087, 3402, 3500, 3528, 3591, 4123, 4221, 4312, 4375, 4914, 4921

Offset: 1

Author

Jun Mizuki (suzuki32(AT)sanken.osaka-u.ac.jp), Jan 17 2005

Keywords

• nonn

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A003325.

Programs

Mathematica

upto[n_] := Block[{t}, Union@ Reap[Do[If[Mod[t = x^3 + y^3, 7] == 0, Sow@t], {x, n^(1/3)}, {y, Min[x, (n - x^3)^(1/3)]}]][[2, 1]]]; upto[5000] (* Giovanni Resta, Jun 12 2020 *)

Extensions

Changed offset from 0 to 1 by Vincenzo Librandi, May 08 2013